I plan to measure rate of flow through CSF shunts in hydrocephalic patients. Flow will be measured using a thermal transfer device of my own invention. The measurement technique is non-invasive, accurate in vivo, and allows serial flow determinations. Flow will be measured in the supine position and following a number of postural and other manipulations which alter the pressure gradient across the shunt. Flow will be correlated with various clinical parameters, and the effects of manipulations assessed. This information will be used to answer several unresolved questions regarding shunt flow in vivo. I hope to use the information obtained from this study in order to establish the thermal transfer device as a clinical tool. Shunt flow measurements should prove valuable in diagnosing and possibly predicting shunt malfunction, in determining the best shunt system for a particular patient and in planning improved shunt systems.